Silane compounds for use as coupling agents and in primer compositions are well known in the art. These coupling agents and compositions are often utilized to bond fillers to thermosetting or thermoplastic resins and substrates. For example, U.S. Pat. Nos. 5,006,573 and 4,800,125, both to Plueddemann, teach the use of silane based coupling agents to improve bonding effectiveness. In particular, U.S. Pat. No. 4,800,125 discloses a composition which includes the reaction product of maleic anhydride with a diamine functional silane compound to improve the performance of such silanes as coupling agents. As discussed in U.S. Pat. No. 4,800,125, such coupling agents are said to promote or improve adhesion stability between fillers or reinforcing agents and polymeric materials, thereby reducing the degradation of such materials, especially after exposure to moisture.
Heretofore, such prior art coupling agents and methods have not been successfully used to bond crosslinked acrylic surfaces to polymeric materials such as polypropylene. This is because crosslinked acrylic materials have rigid, crosslinked bonds that render the material substantially impermeable to other polymers and other substrates. The conventional silane coupling agents have not proved satisfactory to overcome this problem. Another disadvantage associated with much of the silane coupling art has been the inability to prepare an aqueous silane solution for use at a later time. This is due to the initiation of an immediate hydrolysis reaction followed by oligomerization of the silane after preparation of the silane solution, which if not used promptly, results in ineffective bonding or a complete failure in bonding. Consequently, even if prior art silane coupling agents could prove useful for bonding polymers to crosslinked acrylics, which has not been the case, use of such agents would require special manufacturing conditions such that the silane solution would have to be used shortly after preparation.
There has therefore been a long felt need in the art to provide for new techniques and materials for overcoming these and other problems associated with the prior art such that durable, stable polyolefins bonded to crosslinked acrylic articles may be manufactured in a cost effective, reliable manner.